sys_personality: change sys_personality() to accept "unsigned int" instead of u_long

task_struct->pesonality is "unsigned int", but sys_personality() paths use
"unsigned long pesonality".  This means that every assignment or
comparison is not right.  In particular, if this argument does not fit
into "unsigned int" __set_personality() changes the caller's personality
and then sys_personality() returns -EINVAL.

Turn this argument into "unsigned int" and avoid overflows.  Obviously,
this is the user-visible change, we just ignore the upper bits.  But this
can't break the sane application.

There is another thing which can confuse the poorly written applications.
User-space thinks that this syscall returns int, not long.  This means
that the returned value can be negative and look like the error code.  But
note that libc won't be confused and thus errno won't be set, and with
this patch the user-space can never get -1 unless sys_personality() really
fails.  And, most importantly, the negative RET != -1 is only possible if
that app previously called personality(RET).

Pointed-out-by: Wenming Zhang <wezhang@redhat.com>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Oleg Nesterov <oleg@redhat.com>
Cc: "H. Peter Anvin" <hpa@zytor.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

include/linux/personality.h

@@ -12,7 +12,7 @@ struct pt_regs;
 
 extern int		register_exec_domain(struct exec_domain *);
 extern int		unregister_exec_domain(struct exec_domain *);
-extern int		__set_personality(unsigned long);
+extern int		__set_personality(unsigned int);
 
 #endif /* __KERNEL__ */
 

include/linux/syscalls.h

@@ -289,7 +289,7 @@ asmlinkage long sys_capget(cap_user_header_t header,
 				cap_user_data_t dataptr);
 asmlinkage long sys_capset(cap_user_header_t header,
 				const cap_user_data_t data);
-asmlinkage long sys_personality(u_long personality);
+asmlinkage long sys_personality(unsigned int personality);
 
 asmlinkage long sys_sigpending(old_sigset_t __user *set);
 asmlinkage long sys_sigprocmask(int how, old_sigset_t __user *set,

kernel/exec_domain.c

@@ -27,7 +27,7 @@ static struct exec_domain *exec_domains = &default_exec_domain;
 static DEFINE_RWLOCK(exec_domains_lock);
 
 
-static u_long ident_map[32] = {
+static unsigned long ident_map[32] = {
 	0,	1,	2,	3,	4,	5,	6,	7,
 	8,	9,	10,	11,	12,	13,	14,	15,
 	16,	17,	18,	19,	20,	21,	22,	23,
@@ -56,10 +56,10 @@ default_handler(int segment, struct pt_regs *regp)
 }
 
 static struct exec_domain *
-lookup_exec_domain(u_long personality)
+lookup_exec_domain(unsigned int personality)
 {
-	struct exec_domain *	ep;
-	u_long			pers = personality(personality);
+	unsigned int pers = personality(personality);
+	struct exec_domain *ep;
 
 	read_lock(&exec_domains_lock);
 	for (ep = exec_domains; ep; ep = ep->next) {
@@ -70,7 +70,7 @@ lookup_exec_domain(u_long personality)
 
 #ifdef CONFIG_MODULES
 	read_unlock(&exec_domains_lock);
-	request_module("personality-%ld", pers);
+	request_module("personality-%d", pers);
 	read_lock(&exec_domains_lock);
 
 	for (ep = exec_domains; ep; ep = ep->next) {
@@ -135,7 +135,7 @@ unregister:
 }
 
 int
-__set_personality(u_long personality)
+__set_personality(unsigned int personality)
 {
 	struct exec_domain	*ep, *oep;
 
@@ -188,9 +188,9 @@ static int __init proc_execdomains_init(void)
 module_init(proc_execdomains_init);
 #endif
 
-SYSCALL_DEFINE1(personality, u_long, personality)
+SYSCALL_DEFINE1(personality, unsigned int, personality)
 {
-	u_long old = current->personality;
+	unsigned int old = current->personality;
 
 	if (personality != 0xffffffff) {
 		set_personality(personality);
@@ -198,7 +198,7 @@ SYSCALL_DEFINE1(personality, u_long, personality)
 			return -EINVAL;
 	}
 
-	return (long)old;
+	return old;
 }